ISIL militants have claimed that they will attack all countries conducting airstrikes in Syria, saying the US capital of Washington DC is their next priority following the deadly Paris attacks.

The militants made the threats in a new campaign video just days after the Paris attacks, the Daily Mail reported.

“We say to the states that take part in the crusader campaign that, by God, you will have a day God willing, like France’s, and by God, as we struck France in the centre then we swear that we will strike America at its centre in Washington,” one militant said in the video.

One militant speaks in the video. (9NEWS) ()

The video emerged shortly after the Central Intelligence Agency’s director John Brennan warned that the Paris attacks were not a one-off.

“I would anticipate that this is not the only operation that ISIS has in the pipeline,” he said.

ISIL has already claimed responsibility for the series of six attacks across Paris on Friday, November 13, which killed 129 people.

Parisians have held memorials across the city in the days since the attacks, and French President Francois Hollande has vowed that France will continue to be involved in airstrikes against ISIL in Syria.